Liquid esterification for the production of alcohols

Abstract

Purifying and/or recovery of ethanol from a crude ethanol product obtained from the hydrogenation of acetic acid. Separation and purification processes of crude ethanol mixture are employed to allow recovery of ethanol and remove impurities. In addition, the process involves returning acetaldehyde separated from the crude ethanol product to the reactor.

We claim: 
     
       1. A process for producing ethanol comprising:
 hydrogenating acetic acid from an acetic acid feedstream in a first reactor to produce a crude product; 
 removing one or more non-condensable gases from the crude product to yield a liquid stream; 
 reacting the acetic acid and ethanol of the liquid stream in a second reactor, under esterification conditions, to produce an ester enriched stream comprising ethanol and ethyl acetate; and 
 recovering ethanol from the ester enriched stream, wherein the ester enriched stream comprises less than 10 wt. % acetic acid. 
 
     
     
       2. The process of  claim 1 , wherein at least a portion of the recovered ethanol is added to the second reactor. 
     
     
       3. The process of  claim 1 , wherein the liquid stream comprises less than 40 wt. % acetic acid. 
     
     
       4. The process of  claim 1 , wherein the ester enriched stream comprises 0.01 wt. % to 10 wt. % acetic acid. 
     
     
       5. The process of  claim 1 , further comprising providing an alcohol stream to the second reactor. 
     
     
       6. The process of  claim 5 , wherein the alcohol stream comprises less than 50 wt. % of the recovered ethanol. 
     
     
       7. The process of  claim 1 , wherein the conversion of acetic acid in the second reactor is greater than 40%. 
     
     
       8. The process of  claim 1 , wherein the total conversion of acetic acid in the first and second reactor is greater than 90%. 
     
     
       9. The process of  claim 1 , wherein the first reactor comprises a different catalyst than the second reactor. 
     
     
       10. The process of  claim 1 , wherein the first reactor comprises a hydrogenation catalyst selected from the group consisting of platinum/tin, platinum/ruthenium, platinum/rhenium, palladium/ruthenium, palladium/rhenium, cobalt/palladium, cobalt/platinum, cobalt/chromium, cobalt/ruthenium, cobalt/tin, silver/palladium, copper/palladium, copper/zinc, nickel/palladium, gold/palladium, ruthenium/rhenium, and ruthenium/iron. 
     
     
       11. The process of  claim 1 , wherein the acetic acid is formed from methanol and carbon monoxide, wherein each of the methanol, the carbon monoxide, and hydrogen for the hydrogenating step is derived from syngas, and wherein the syngas is derived from a carbon source selected from the group consisting of natural gas, oil, petroleum, coal, biomass, and combinations thereof. 
     
     
       12. The process of  claim 1 , wherein the second reactor comprises an acid catalyst. 
     
     
       13. The process of  claim 1 , wherein the first reactor operates a temperature from 125° C. to 350° C. and the second reactor operates a temperature from 10° C. to 150° C., wherein the operating temperature of the second reactor is lower than the operating temperature of the first reactor. 
     
     
       14. A process for producing ethanol comprising:
 providing a crude ethanol product comprising ethanol, ethyl acetate, non-condensable gases, and acetic acid; 
 removing one or more non-condensable gases from the crude product to yield a liquid stream; 
 reacting the acetic acid and ethanol of the liquid stream in a reactor, under esterification conditions, to produce an ester enriched stream comprising ethanol and ethyl acetate; and 
 recovering ethanol from the ester enriched stream, wherein the ester enriched stream comprises less than 10 wt. % acetic acid. 
 
     
     
       15. A process for producing ethanol comprising:
 hydrogenating acetic acid from an acetic acid feedstream in a first reactor to produce a crude ethanol product; 
 separating a portion of crude ethanol product to produce an aqueous stream comprising water and a liquid crude ethanol product stream; 
 directing in the liquid crude ethanol product stream to a second reactor to react the acetic acid and the ethanol to produce an ester enriched stream; and 
 recovering ethanol from the ester enriched stream, wherein the ester enriched stream comprises less than 10 wt. % acetic acid. 
 
     
     
       16. The process of  claim 15 , wherein the aqueous stream comprises at least 75% of the water from the crude product. 
     
     
       17. The process of  claim 15 , wherein the step of separating a portion of crude product is conducted by passing the portion of crude product through a membrane to yield a permeate comprising the aqueous stream and a retentate comprising the liquid crude ethanol product stream. 
     
     
       18. The process of  claim 15 , wherein the step of separating a portion of crude product is conducted by feeding the portion of crude product to a pervaporation unit. 
     
     
       19. The process of  claim 15 , wherein at least a portion of the recovered ethanol is added to the second reactor. 
     
     
       20. The process of  claim 15 , wherein the liquid crude ethanol product stream comprises less than 40 wt. % acetic acid. 
     
     
       21. The process of  claim 15 , wherein the ester enriched stream comprises from 0.01 wt. % to 10 wt. % acetic acid. 
     
     
       22. A process for producing ethanol comprising:
 providing a crude ethanol product comprising ethanol, ethyl acetate, water, and acetic acid; 
 separating a portion of crude ethanol product to produce an aqueous stream comprising water and a liquid crude ethanol product stream; 
 reacting the acetic acid and ethanol of the liquid crude ethanol product stream in a reactor, under esterification conditions, to produce an ester enriched stream; and 
 recovering ethanol from the ester enriched stream.